The present invention relates to machines for shaping objects made of glass or some other material and relates in particular to a work head for these machines which is very precise and very robust.
At the present time, ever increasing precision is being demanded of glassware intended, for example, for pharmaceutical laboratories. Now, this quality goes hand in hand with the precision of the components of the machine that manufactures these products and more particularly the gripper which holds these glass objects while they are being shaped.
Most current work heads for these handling operations comprise pincher fingers articulated to the body of the head and actuated by an operating member sliding along and on the outside of the body of the head. The great drawback with this type of head is that the bearing which holds the head is relatively distant from the end of the head because the very design of these heads means that the member for operating the pincher fingers and its return spring have to be fitted between the head and the bearing. In consequence, errors in the manufacture of the rolling bearings of the bearing, and errors in the machining of the various constituent parts of the head are amplified by the lever arm phenomenon.
Another drawback with this type of work head is that the pincher fingers are pinched onto the pivots by binding screws. Vibrations of the machine or a chance blow to a pincher finger have the effect of decalibrating the gripping of an object that is being handled. This constant decalibration of the pincher fingers costs the users of machines equipped with this type of head dearly, not only in terms of the scrapping of defective products completed before the technician noticed the defect with the head in question, but also in terms of machine downtime and the cost of labor for repairing this head.
The object of the present invention is to overcome these drawbacks which result in numerous machine stoppages for repair and recalibration of the gripper so that the production quality can be kept within acceptable standards.
This object is achieved, in accordance with the invention, by virtue of a work head as defined in the claims.
More specifically, a first feature of the device according to the invention lies in the fact that the member for operating the pincher elements and its return spring are mounted inside the body of the head. In this way, the bearing that holds the gripper head is very close to the end of the head, this making it possible to avoid the phenomenon of amplifying the errors in the machining of the constituent parts of the pincher elements. Furthermore, the operating member is hollow to allow the passage of a tube or object that is to be shaped.
A second feature of the invention lies in the fact that each pincher element consists of just one single piece, this preventing any relative displacement of the two arms of the pincher element.
A third feature of the invention lies in the fact that each pincher element can be adjusted individually by a set screw which presses directly on the operating member. Thanks to this adjustment of the pincher elements, it is possible for the product gripped in the head to be perfectly centered.
A fourth feature of the invention lies in the fact that each head and its bearing form a unit which can be removed from the machine as a single entity so that the head can be calibrated on a bench and thus avoid extensive downtime of the production machine.
The features and advantages of the invention will emerge more clearly from the appended drawings and the description which follows.